The present invention relates to removal of thrombus from arteries. More generally, it relates to a system and method for widening passages in the human body.
Within the human body are various passages which convey fluids. Material may build up on the walls of such passages such that partially blockages may occur. Indeed, such partially blockages may eventually become complete blockages. Whether the blockages are partial or complete, there usually are adverse health consequences.
In the cardiovascular system in particular, a vein or artery may be partially or completely blocked. The veins or venous blood vessels may be blocked (i.e., meaning partially or completely) by a soft blood clot called a thrombus. The arteries or arterial blood vessels may be blocked by a thrombus. In either the vein or artery, plaque or other such blockages should be treated using one or more medical procedures.
The following patents are noted:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Auth 4,445,509 May 1, 1984 Auth 4,646,736 March 3, 1987 Summers 4,850,957 July 25, 1989 Stack et al 4,867,156 Sept. 19, 1989 Auth 4,990,134 February 5, 1991 Stack et al 5,059,211 October 22, 1991 Stack et al 5,306,286 April 26, 1994 Auth et al 5,314,407 May 24, 1994 Auth et al 5,364,393 November 15, 1994 Cragg 5,370,653 December 6, 1994 ______________________________________
The Stack patents disclose a catheters for removing plaque from the wall of an artery using blade elements and devices to work with such cutting catheters.
The Auth patents show various structures for breaking up thrombus. Diamond dust covered abrasive devices, a cutting tool with spirally shaped cutting flutes, and electrical ablation are among the techniques disclosed.
The Cragg patent and the Summers patent both show cutting catheter systems and methods. Cragg has rotatable soft flexible bristles, whereas Summers has a cutting arrangement with a continuous filament brush and an alternate cutting blade design.
Although the above and other designs may have been somewhat useful, they are often subject to one or more of several disadvantages.
Prior cutting devices often must be sized to fit the particular passage which is being treated. In other words, one must use a different size cutter for different size vessels. Disadvantageously, one must then keep more than one cutter and determine the correct size before putting the cutter into the patient such that the correct size cutter is used. Use of a cutter that is too small does not remove all of the plaque or other built up material. Use of a cutter that is too large increases the chances of damaging healthy tissues on the wall of the passage.
Some prior devices for cutting or removing material from the walls of passages in a patient are constructed such that they may damage healthy tissues on the wall of the passage even if they are the right size. Depending on the characteristics of the blocking material, adjacent healthy tissue, and the cutting device (for example, if the cutting device is too rigid), damage may occur when cutting.
A further problem with some prior arrangements is that materials removed from the wall of a blood vessel for example can create problems downstream from the original blockage. Removed materials can resettle downstream and create a partial or complete blockage at a new location. Depending on the size of material pieces, a heart attack, stroke, or other health problems can result from removing blood vessel obstructing material. Some techniques use chemical solutions to try to dissolve the pieces. Depending on the chemical used, this may require that the passage be blocked by a balloon for a considerable period of time. A catheter controlled balloon may be used downstream from where material is being removed. The balloon prevents removed material from passing by it until the material is dissolved. Suction devices have also been used for removing material.